Thermoplastic polymers and mixtures of different thermoplastic polymers play an important part as engineering plastics. Most of these polymers and compositions contain, in addition to residual monomers, residual solvents and oligomeric additives of low molecular weight imparting to them certain properties, e.g. stabilizers, pigments, mold release agents, flame-proofing agents and antistatic agents.
Owing to their volatility at the conventional processing temperatures (generally 200.degree. to 350.degree. C.) such additives of low molecular weight partly segregate from the thermoplastic compositions loss their effectiveness and impair quality, i.e. cause surface faults on the shaped articles, deposits on injection molding tools and unpleasant odors.
It has now been discovered that specially prepared magnesium aluminum silicates are capable of binding additives of low molecular weight in polymers to such an extent as to ensure that the latter do not evaporate during processing. These carrier materials do not impair the characteristics of thermoplastic polymers so that e.g. their toughness decreases slightly, the surface is preserved, resistance to chemicals and heat distortion temperature are improved. Also flame-proofing agents, of which in general major quantities are required, remain at processing temperatures in the polymer and can be fully effective in case of fire.